Axial flow pump

ABSTRACT

An axial flow pump includes a housing supporting a tubular, electric motor driven pump body for rotation about an axis, and a plurality of impeller units detachably supported within the tubular pump body. The impeller units are constructed to provide a substantially unobstructed axial pumping passage through the pump body and are removable from the pump body without requiring disassembly of the pump body or the housing.

United States Patent 1 McFarlin AXIAL FLOW PUMP [75] Inventor: Stanley B. McFarlin, Jeromesville,

Ohio

[73] Assignee: The Gorman-Rupp Company,

Cleveland, Ohio [22] Filed: Sept. 22, 1970 [21] Appl. No.: 74,398

[52] US. Cl ..417/356 [51] Int. Cl..'.... ..F04b 35/04 [58] Field of Search ..417/356; 310/61; 415/72 [56] References Cited UNITED STATES PATENTS 1,071,042 8/1913 Fuller ..417/356 X 2,181,677 11/1939 Whittome et a1 ..417/356 March 6, 1973 2,500,400 3/1950 Cogswell ..417/356 2,631,543 3/1953 Richmond v.417/3156 3,105,444 10/1963 Ghougasian ..415/72 Primary ExaminerWilliam L. Freeh Assistant Examiner-John T. Winburn Att0mey-Watts, l-loffmann, Fisher & Heinke [5 7] ABSTRACT An axial flow pump includes a housing supporting a tubular, electric motor driven pump body for rotation about an axis, and a plurality of impeller units detachably supported within the tubular pump body. The impeller units are constructed to provide a substantially unobstructed axial pumping passage through the pump body and are removable from the pump body without requiring disassembly of the pump body or the housing.

16 Claims, 4 Drawing Figures PATENTEUHAR 6 m 3,719,436

INVENTOR v 5T4NLE7/ 5. MCFAEL/N PATENTEDHAR 6W SHEET 2 BF 3 INVENTOR 5774 A/LEY 5, M: FAEL/N Wm, m

ATTOENEYfi.

PATENTEUHAR 61973 $719,432;

SHEET 3 OF 3 INVENTOR. STANLEY 5. MFAEL/A/ 14 TTOEA/E 7 5 AXIAL FLOW PUMP BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to pumps, and more particularly to axial flow pumps.

2. The Prior Art The prior art has proposed axial flow pumps in which impellers forced liquid axially through a tubular rotatable pumping body. In some prior art pumps, the tubular pump body carried an impeller at one end so that the tubular body formed an inlet passageway for the impeller. In other proposals, impellers were supported in the pump body itself on central shafts or similar supports.

These proposals required nearly complete disassembly of the pump body or the pump body housing in order to service or replace an impeller. When these axial flow pumps were used to pump liquids containing significant quantities of debris, such as in sewage, they tended to clog because debris jammed against obstructions, such as the impeller supporting shafts, in the flow path through the pumps. Servicing often required the pumps to be torn down to gain access to the debris jammed in the flow passages. The pumps also had to be torn down in order to replace impellers which were damaged and/or eroded by abrasive or chemically active materials in the pumped liquid. Servicing such pumps was expensive, time consuming, complicated and often unpleasant for the serviceman. At least partly because of the foregoing problems, axial flow pumps have not been widely commercialized, particularly when used to pump liquids containing debris and/or abrasive particulate matter.'

Electric motor driven centrifugal pumps having the motor windings and pump mechanism in a common housing have been widely used. The motor windings in these pumps were frequently hermetically sealed, particularly where the pump was likely to be submerged. When the motor windings were sealed, heat dissipation was retarded and the motors tended to overheat.

It was proposed to dissipate this heat by transferring it to the pumped liquid. In some proposals, the pump housings were cast with flow passages in them for directing pumped liquid through the housing close to the motor windings. These passageways were often tortuous, thus tending to become clogged and/or eroded by particles in the pumped fluid. Furthermore, the housing castings were expensive and complex.

In some proposals, the motor windings were not sealed and heat was dissipated from them by directing pumped liquid onto the windings. These proposals could not be employed in circumstances where abrasive materials were likely to be present in the pumped liquid or where chemically active elements might be pumped, since the motors would be damaged.

Electric motor driven pumps were sometimes damaged by rotating the impellers opposite to the designed pumping direction. Many pumps of this type had impellers which were screwed onto their-drive shafts. If a drive motor was incorrectly wired, the impeller tended to screw off of its shaft resulting in damage to'the pump.

In summary, prior art axial flow pumps have been subject to clogging or erosion due to debris and particulate matter in the pumped liquid; have been difficult to service when clogged or when impeller needed repair; were either subject to overheating due to inadequate heat dissipation from electric drive motors or employed complex, expensive motor cooling arrangements; and were sometimes subject to damage when the impellers were rotated reversely from their intended direction of rotation.

SUMMARY OF THE INVENTION The present invention provides a new and improved axial flow pump characterized by a simple and inexpensive construction which enables impeller servicing or replacement without disassembly of the pump. The new pump also provides for heat dissipation from an electric drive motor to the pump effluent without routing the effluent through housing passageways and without exposing the motor windings to the pumped liquid.

The new pump is particularly useful in applications requiring large flow rates of pumped liquid at moderate pressures, is adapted to operate submerged and can readily pump liquids which may contain substantial amounts of debris and/or particulate abrasive material.

In a preferred embodiment, the new pump includes a housing assembly defining a pump inlet port and a pump discharge port and a rotatable pump body supported in the housing. Impeller units are detachably connected to the pump body and can be removed and replaced through the inlet or discharge ports without tearing down the housing or the pump body.

In the preferred embodiment, the pump is driven by an induction motor having an encapsulated stator in the housing. The housing provides an impervious container for the stator and the pump can be submerged without exposing the stator to the liquid. The pump body forms the motor rotor and provides an axial pumping passage in which the impeller members of the pump are mounted.

The construction of the pump body and housing promotes heat dissipation from the stator and rotor windings without exposing the windings to the pumped liquid which otherwise might damage them. In the preferred construction, the pump body is supported in the housing by bearings which are spaced axially apart. Seal assemblies are disposed between the housing and the pump body axially outwardly of the bearings. A

chamber is thus formed between the pump body and the housing. The chamber contains a suitable liquid such as transformer oil which, when the motor is operating, circulates in the chamber. The oil picks up heat from the rotor windings and from the chamber walls adjacent the stator windings and transfers the heat to the liquid flowing through the pump via the pump body. The circulating oil also lubricates the outer periphery and impeller blades integral with the shroud member.

The shroud members may be attached in the pump body by commercially available adhesive materials capable of transmitting sufficient torque for pumping yet readily releasing the impeller when desired. This mode of connection enables the pump to operate in either direction of rotation to reverse the flow direction of the pumped liquid, as might be required in a pipe line installation. Other modes of connection such as interengaging splines or screw threads may be employed.

The pumping passage of the new pump is substantially unobstructed by impeller or rotor supporting parts so that debris in the pumped liquid does not tend to clog the pump. If the pump does clog, the unobstructed passage permits dislodgment of the offending debris without requiring disassembly of the pump.

In one embodiment, the impeller blades extend inwardly from the inner periphery of the shroud member toward the axis of rotation of the pump body. The blades terminate short of the center of the axis of rotation and are spaced from each other at their tips so that the pump body is open along its axis of rotation.

In another preferred form, the impeller blades are formed by an auger-like member which is supported solely by the surrounding shroud member and has no central supporting body or shaft.

Several impeller units may be serially supported in the pump body. These impeller members can be constructed to provide for compounding if desired by providing impeller blades having varying pitches proceeding through the pump body.

A principal object of the present invention is the provision of a new and improved axial flow pump which is of simple, inexpensive construction, employs a substantially unobstructed pumping passage to minimize clogging and which, if clogged, is easily cleared without requiring disassembly.

Another object of the present invention is the provision of a new and improved axial flow pump having one or more impeller units which are detachably connected to a rotatable pump body and which impeller units can be removed and replaced through a housing port without requiring disassembly of either the pump housing or the rotatable pump body. V

Still another object of the invention is the provision of a new and improved axial flow pump driven by an electric motor which is hermetically sealed and wherein heat from the motor is transferred to the pumped liquid through a heat transfer medium contained in a chamber between the pump body and the housing.

Other objects and advantages of the present invention will become apparent from the following detailed description made with reference to the accompanying drawings which form a part of the specification.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross sectional view of a pump embodying the present invention;

FIG. 2 is an end view of the pump of FIG. I seen from the plane indicated by the line 2-2 of FIG. 1;

FIG. 3 is a fragmentary cross sectional view of another preferred embodiment of the new pump seen approximately from the line 33 of FIG. 4; and,

FIG. 4 is an end view seen from the left end of FIG. 3.

4 DESCRIPTION or PREFERRED EMBODIMENTS One preferred embodiment of an axial flow rotary pump 10 constructed according to the present invention is illustrated in FIGS. 1 and 2. The pump 10 is usable in applications where large flow rates of pumped liquid are required at moderate pressures. The pump can be submerged and is particularly suited to pump sewage or liquid which may contain substantial amounts of debris and/or abrasive particulate matter, etc. The pump 10 includes a housing assembly 12 defining aninlet port 14 and a discharge port 16. A pump body 18 is supported by the housing assembly 12 for rotation about an axis 19. The pump body 18 carries impeller units 20 which rotate with the pump body to propel liquid through the pump along the axis 19. An alternating current induction motor 22 drives the pump body.

The housing 12 is a simple, inexpensive assembly which supports the pump body 18 while providing a hermetically sealed container for the stator of the motor 22. The housing 12 includes a pair of mating identical end cup members 24, 26; a thin cylindrical sleeve 27 connected between the end cup members along the inner periphery of the housing; and bearing support members 28, 30 which are supported at opposite axial ends of the end cup members 24, 26, respectively.

The mating end cups 24, 26 and the sleeve 27 form an annular enclosure in which the stator 32 of the motor 22 is hermetically sealed. Referring to FIG. 1, each of the end cup members is a cast body having an annular axially facing lip 33 at its outer periphery and a base 34 having a cylindrical opening 34a extending through it. Each end cup 24, 26 has a wall portion 35 extending radially from the base 34. The wall 35 has a bossed area 35a surrounding an opening 36.

The stator 32 is of conventional construction including a stack of laminations 32a and stator windings 32b. The stator 32 is encapsulated in a mass 37 of potting compound, which may be any suitable epoxy. The potting compound completely fills the enclosure defined by the housing. A power cable 38 for the stator windings extends through the opening 36 in the end cup member 26. The opening 36 in the end cup member 24 is sealed closed by the potting compound.

The method of assembling the end cups 24, 26, sleeve 27 and the stator 32 is simple and requires minimal labor. The end cup member 24 is placed on a suitable horizontal surface with its lip 33 facing upwardly. The opening 36 is plugged and the sleeve 27 is pressed into place along the inner periphery of the base 34. A small shoulder 39 may be provided in the base for receiving the sleeve 27, if desired. Uncured potting compound is then poured into the end cup member 24. The stack of laminations 32a has an outer periphery which tits snugly against the inner periphery of the end cups, and the stator 32 is pressed into the end cup member 24. The end cup member 26 is then placed over the sleeve 27 and the end cup member 24, and pressed onto the stator 32 until the cup lips 33 mate and the sleeve 27 is engaged by the shoulder 39 in the end cup 26. The power cable 38 is pulled through the opening 36 in the end cup 26 and the remaining space in the housing is filled with potting compound which is introduced through the opening 36 around the power cable 38. l

The housing may be placed under vacuum pressure to assure complete filling with potting compound after which the compound is cured.

The end cups 24, 26 are maintained in mating engagement by the cured potting compound; however the lips 33 can be welded or cemented together at their juncture if desired.

The support members 28, 30 provide bearing supports for the pump body 18 and also enable connection of accessory components to the pump. The support members 28, 30 are identical and each includes a body 40 having a flange 42 engaging the base 34 of the adjacent housing end cup. The base 34 .of each end cup carries a plurality of projecting studs 43 each having a threaded end extending through a bore in the flange 42. The support members are each bolted to the housing 12 by nuts which are threaded on the studs 43. The central openings through the bodies 40 of the support members 28, 30 define the housing inlet and discharge ports 14, 16, respectively.

The body 40 projects into the adjacent end cup base 34 and a suitable seal arrangement 46 is disposed between them. The projecting end of the body 40 defines an annular bearing seat 47. A bearing assembly 48 has its outer race engaged on the seat 47. The pump body 18 is journalled in the bearing assemblies 48.

Various accessory components can be detachably connected to the support members 28, 30. The bodies 40 are each provided with tapped holes arranged about the axis of rotation of the pump body 18 so that parts can be screwed onto the bodies 40 and thus attached to the housing. In the embodiment illustrated in FIG. 1, a pipe coupling member 49 is attached to the support member 30. The coupling member is provided with internal pipe threads into which a pump discharge pipe (not shown) can be screwed. The pipe coupling member is illustrated by way of example and accordingly is shown in broken lines.

The support member 28 at the opposite end of the pump has a pair of identical bracket-like legs 50, 52 (FIG. 2) attached to it. The-legs 50, 52 are utilized for handling the pump prior to installation. Where the pump is installed in a submerged location, the legs support the pump in an upright position with the inlet port 14 spaced from the supporting surface so that flow through the inlet is not restricted.

The pump body 18 forms the rotor of the motor 22 and provides an axial pumping passage in which the impeller units are supported. The body 18 includes a hollow rotatable shaft 64 having an axial bore 65 extending through it along the axis 19. The rotor assembly 66 of the motor 22 is affixed on the external periphery of the shaft 64. The rotor assembly is conventional and includes a stack of laminations 66a fixed to the shaft and rotor windings 66b.

The shaft 64 is rotatably supported by the bearing assemblies 48 which are positioned at opposite axial ends ofthe rotor 66. The pump body 18 is freely rotatable with respect to the housing 12 and when the motor 22 is energized, the pump body 18 is driven by the motor. The motor 22 is reversible so that the pump body 18 can be driven in either rotational direction to reverse the direction of flow of the pumped liquid.

The construction of the pump body 18 and the housing 12 promotes heat dissipation from the stator and rotor windings without exposing the windings to pumped liquid which might otherwise damage them. More particularly a sealed annular chamber generally designated by the reference character is formed between the pump body and the housing. The chamber 70 contains a fluid which circulates in the chamber when the motor is operating and carries heat from the motor windings to the pump body which is cooled by the pumped liquid. The axial ends of the chamber 70 are formed by seal assemblies 74, 76. As is best seen in FIG. 1, the seal assemblies 74, 76 are each supported between the housing 12 and the pump body 18 axially outwardly of the adjacent respective bearing assembly 48. The seal assemblies 74, 76 may be of any suitable construction but are schematically shown as including a stationary sealing ring 77 which is sealingly engaged with a shoulder 78 on the body 40, and a rotatable sealing ring 79 which is sealingly engaged with the shaft 64. The adjacent faces of the sealing rings 77, 79 are engaged to form a running seal between the housing 12 and the pump body 18.

The chamber 70 is preferably filled with transformer oil which dissipates heat and lubricates the bearings and seal faces. When the motor 22 is energized, the oil in the chamber circulates vigorously in the chamber. Heat from the stator 32 is conducted to the oil through the sleeve 27. The rotor windings dissipate heat directly to the oil. The shaft 64 has a relatively small wall thickness and provides a heat sink from which heat is transferred from the oil in the chamber 70 to the pumped liquid.

The impeller units 20 are detachably mounted in the pumping passage defined by the bore 65 and each impeller unit is removable and replacable through the adjacent inlet or discharge port without loosening or removing portions of the housing assembly 12 or any part of the pump body 18. As is shown in FIG. 1, two impeller units 20a, 20b are mounted in the shaft 64 at opposite axial ends. The impeller units 20a, 20b are identical and accordingly only the impeller unit 20a is described in detail. The unit 20a includes a cylindrical shroud member 80 which is seated in the bore 65 at the inlet end of the shaft 64. Four impeller blades 82 are integral with the shroud member and project radially inwardly from the shroud member towards axis 19. The blades terminate short of the axis 19 and the blade tips are spaced from each other so that the axis of rotation 19 extends uninterrupted through the pumping passage. The blades 82 are supported solely at their juncture with the shroud member 80.

The shroud member 80 has a radially outwardly extending shoulder 84 which seats against the end of the annular shaft 64. The shroud member is detachably connected to the shaft along its external periphery by an adhesive material which when hardened transmits sufficient torque to enable effective pumping of the liquid by the impeller but which frees the shroud member for removal when desired. These adhesives permit reversing the direction of rotation of the pump body without loosening the impeller units. For example, such adhesives can be broken by sharply rapping the shroud member at various locations about its periphery. Other fastening devices can be employed to maintain the impellers in place on the interior of the shaft such as splines or screw threads, etc.

FIGS. 3 and 4 show a pump employing alternate forms of impeller units. Three alternate impeller units 120, 122 and 124 are detachably fixed in the shaft 64. The impeller units 120, 124 at opposite ends of the shaft 64 each include identical shroud members 126, 128, respectively. These shroud members each have an annular radially outwardly extending shoulder 130 which engages the annular end of the shaft. The shroud members 126, 128 are suitably connected to the shaft in the manner described above.

The impeller member 134 in the impeller unit 120 is an auger-like element formed by a sheet of material which is helically twisted and attached to the shroud member 124 at its edges. The auger-like member has a uniform cross sectional thickness and has no central supporting shaft or the like. The sole support for the auger member is formed by the surrounding shroud member.

The impeller units of FIGS. 3 and 4 have a decreasing pitch, or bite, proceeding through the pump from the inlet port to the outlet port. This produces a staging or compounding effect which increases the pump discharge pressure. The auger-like impeller member 136 of the impeller unit 124 is substantially the same as the auger 134 except that its pitch or lead is smaller.

The central impeller unit 122 is spaced from the impeller units 120, 124 by axial spacers 138. The unit 122 includes a cylindrical shroud member 140 and an auger-like impeller member 142. The shroud member 140 is suitably fixed to the shaft 64. The impeller member 142 is substantially the same as the impellers of the units 120, 124 except that its lead is slightly less than that of the impeller 134. The impeller unit 122 is removable from either end of the pump.

Since the auger-like impellers of the unitsl20, 122, 124 have no central supporting shafts or equivalent central supports, the pump passage is relatively unobstructed. Hence, debris in "the pumped liquid does not tend to hang up in the pump passage. The unobstructed pumping passage is readily accessible for cleaning out without disassembling the pump if the passage does become clogged by debris since the debris is easily dislodged by a cleaning tool inserted through either the inlet port or the discharge port.

It can now be seen that a new and improved axial flow pump has been provided and that the objects enumerated and others have been accomplished. Although two preferred constructions have been illustrated and described in considerable detail, the present invention is not to be considered limited to the precise constructions shown. It is intended to cover all adaptations, modifications and uses of the invention which come within the scope of the appended claims.

What is claimed is:

I. A fluid pump having an inlet and a discharge and comprising:

a. a housing;

b. a hollow tubular body supported by said housing for rotation about an axis, said body defining first and second end openings and a flow passage extending therethrough along said axis between said end openings;

c. drive means for rotating said body about said axis;

and,

d. impeller means supported by said body for propelling fluid through said flow passage defined by said tubular body;

e. said impeller means comprising at least an impeller detachably connected to an internal peripheral portion of said body member and axially removable from said body through one of said first or second end openings of said body.

2. A pump as claimed in claim 1 wherein said pump body comprises a hollow shaft, said impeller comprising a shroud member detachably connected to said internal peripheral portion of said shaft for rotation with said shaft about said axis, and at least an impeller member in said passage supported solely by said shroud member at the juncture of said shroud member and said impeller member, said shroud member and said impeller member removable as a unit from said shaft via one of said end openings.

3. A pump as claimed in claim 2 wherein said impeller member is defined by a blade projecting toward said axis from said shroud member, said blade terminating radially outwardly from said axis whereby said passage is unobstructed along said axis.

4. A pump as claimed in claim 2 wherein said impeller member comprises an auger defined by a helically formed sheet supported by said shroud member at its edges and devoid of a central supporting member.

5. A pump as claimed in claim 2 including a plurality of said impellers each detachablyconnected to an internal peripheral portion of said shaft at axially spaced locations along said passage, each impeller removable from said passage through one of said first or second openings.

6. A pump as claimed in claim 5 wherein the impeller 7 members of successive impellers have decreasing pitches proceeding along said passage from one of said end openings toward said other end opening.

7. A pump as claimed in claim 2 wherein said housing defines inlet and discharge ports aligned with said flow passage, and said shroud member has a smaller diametrical extent than the diametrical extent of at least one of said inlet or discharge ports, said shroud member removable from said housing through said at least one inlet or discharge port.

8. A pump as claimed in claim 1 wherein said drive means for rotating said body about said axis comprises an electric motor having a stator in said housing and a rotor formed by said body.

9. A pump as claimed in claim 8 and further including seal means between said body and said housing at axially spaced locations, said seal means, said body and said housing defining a chamber surrounding said body, and further including fluid in said chamber, said fluid circulating when said body rotates to transfer heat to pumped fluid in said passage from said motor.

10. A pump as claimed in claim 9 wherein said h0us ing comprises first and second identical end cups each having an annular lip at an outer periphery and an annular base at an inner periphery, said annular lips engaging along the outer periphery of said housing and a sleeve extending between said bases along an inner periphery of said housing, and means for hermetically sealing said stator in said housing between said end cups and said sleeve.

11. A pump as claimed in claim 10 wherein said housing further includes first and second identical support members connected to respective bases of said end caps, said support members associated with bearings supporting said pump body, said housing being symmetrical about the juncture of said lips.

12. A pump comprising:

a. an electric motor defined by a generally cylindrical stator assembly and a rotor member supported for rotation about an axis extending through said stator assembly;

. a generally cylindrical pumping passage defined by said rotor member, said pumping passage extending through said rotor member along said axis and defining a first opening at one end of said rotor member and a second opening at an opposite end of said rotor member with pumped fluid passing through said passage via said end openings;

c. impeller means in said pumping passage and disposed at least in part between said first and second rotor member openings, said impeller means being operative to create a flow of fluid through said pumping passage via saidopenings when said rotor member is rotated about said axis; and,

d. connecting means between said impeller means and said rotor member for enabling removal and replacement of said impeller means from said pumping passage through one of said rotor member openings.

13. A pump as claimed in claim 12 wherein said impeller means comprises impeller members projecting radially into said pumping passage, said impeller members defining projecting tip portions which are spaced radially outwardly from said axis.

14. A pump as claimed in claim 12 wherein said impeller means comprises an anger defined by a helically formed sheet-like member, said sheet-like member supported in said passage along side edges thereof.

15. A pump as claimed in claim 12 wherein said connecting means comprises at least a member between said impeller means and said rotor member said at least one member being detachably connected to at least one of said impeller means or rotor member.

16. A pump 'as claimed in claim 15 wherein said member of said connecting means is detachably connected to said rotor member by an adhesive material. 

1. A fluid pump having an inlet and a discharge and comprising: a. a housing; b. a hollow tubular body supported by said housing for rotation about an axis, said body defining first and second end openings and a flow passage extending therethrough along said axis between said end openings; c. drive means for rotating said body about said axis; and, d. impeller means supported by said body for propelling fluid through said flow passage defined by said tubular body; e. said impeller means comprising at least an impeller detachably connected to an internal peripheral portion of said body member and axially removable from said body through one of said first or second end openings of said body.
 1. A fluid pump having an inlet and a discharge and comprising: a. a housing; b. a hollow tubular body supported by said housing for rotation about an axis, said body defining first and second end openings and a flow passage extending therethrough along said axis between said end openings; c. drive means for rotating said body about said axis; and, d. impeller means supported by said body for propelling fluid through said flow passage defined by said tubular body; e. said impeller means comprising at least an impeller detachably connected to an internal peripheral portion of said body member and axially removable from said body through one of said first or second end openings of said body.
 2. A pump as claimEd in claim 1 wherein said pump body comprises a hollow shaft, said impeller comprising a shroud member detachably connected to said internal peripheral portion of said shaft for rotation with said shaft about said axis, and at least an impeller member in said passage supported solely by said shroud member at the juncture of said shroud member and said impeller member, said shroud member and said impeller member removable as a unit from said shaft via one of said end openings.
 3. A pump as claimed in claim 2 wherein said impeller member is defined by a blade projecting toward said axis from said shroud member, said blade terminating radially outwardly from said axis whereby said passage is unobstructed along said axis.
 4. A pump as claimed in claim 2 wherein said impeller member comprises an auger defined by a helically formed sheet supported by said shroud member at its edges and devoid of a central supporting member.
 5. A pump as claimed in claim 2 including a plurality of said impellers each detachably connected to an internal peripheral portion of said shaft at axially spaced locations along said passage, each impeller removable from said passage through one of said first or second openings.
 6. A pump as claimed in claim 5 wherein the impeller members of successive impellers have decreasing pitches proceeding along said passage from one of said end openings toward said other end opening.
 7. A pump as claimed in claim 2 wherein said housing defines inlet and discharge ports aligned with said flow passage, and said shroud member has a smaller diametrical extent than the diametrical extent of at least one of said inlet or discharge ports, said shroud member removable from said housing through said at least one inlet or discharge port.
 8. A pump as claimed in claim 1 wherein said drive means for rotating said body about said axis comprises an electric motor having a stator in said housing and a rotor formed by said body.
 9. A pump as claimed in claim 8 and further including seal means between said body and said housing at axially spaced locations, said seal means, said body and said housing defining a chamber surrounding said body, and further including fluid in said chamber, said fluid circulating when said body rotates to transfer heat to pumped fluid in said passage from said motor.
 10. A pump as claimed in claim 9 wherein said housing comprises first and second identical end cups each having an annular lip at an outer periphery and an annular base at an inner periphery, said annular lips engaging along the outer periphery of said housing and a sleeve extending between said bases along an inner periphery of said housing, and means for hermetically sealing said stator in said housing between said end cups and said sleeve.
 11. A pump as claimed in claim 10 wherein said housing further includes first and second identical support members connected to respective bases of said end caps, said support members associated with bearings supporting said pump body, said housing being symmetrical about the juncture of said lips.
 12. A pump comprising: a. an electric motor defined by a generally cylindrical stator assembly and a rotor member supported for rotation about an axis extending through said stator assembly; b. a generally cylindrical pumping passage defined by said rotor member, said pumping passage extending through said rotor member along said axis and defining a first opening at one end of said rotor member and a second opening at an opposite end of said rotor member with pumped fluid passing through said passage via said end openings; c. impeller means in said pumping passage and disposed at least in part between said first and second rotor member openings, said impeller means being operative to create a flow of fluid through said pumping passage via said openings when said rotor member is rotated about said axis; and, d. connecting means between said impeller means and said rotor member for enabling removal and replAcement of said impeller means from said pumping passage through one of said rotor member openings.
 13. A pump as claimed in claim 12 wherein said impeller means comprises impeller members projecting radially into said pumping passage, said impeller members defining projecting tip portions which are spaced radially outwardly from said axis.
 14. A pump as claimed in claim 12 wherein said impeller means comprises an auger defined by a helically formed sheet-like member, said sheet-like member supported in said passage along side edges thereof.
 15. A pump as claimed in claim 12 wherein said connecting means comprises at least a member between said impeller means and said rotor member said at least one member being detachably connected to at least one of said impeller means or rotor member. 